Method for feeding a closed liquid system

ABSTRACT

A method for automatically feeding a closed liquid system from a liquid source according to need by creating between the liquid source and the closed liquid system a load buffer formed from liquid, in which between the liquid source and the feed buffer only liquid flow in the direction of the feel buffers is allowed and from the feed buffer to the closed liquid system only drorpwise liquid transport is admitted. The feed buffer can be realized with a cylindrical drip feeder with inlet, outlet and freely movable plunger, which can close the outlet in an abutting position while leaving clear a minuscule leakage channel and is provided with a passage with a non-return valve in the direction of the inlet. Such a drip feeder can, with or without insertion of a storage container for liquid, be connected with, for instance, a liquid system, such as a central heating system with pipe system, boiler and expansion tank.

[0001] The present invention relates to a method for automatically feeding a closed liquid system, such as, for instance, a central heating system or another heat exchange or process system designed as a closed liquid circuit, from a liquid source according to need, in which system a feed buffer formed from liquid is created and between the liquid source and the feed buffer only liquid flow in the direction of the feed buffer is allowed. The invention also relates to a drip feeder that can be used to realize such a method and a heating system in which the method and the drip feeder are used.

[0002] A method as described above is known from WO-A-00/19149. In a deaerating chamber therein a liquid stock is maintained, which is made up according to need via a float-controlled valve from a liquid source, more in particular a public water supply system. In such a method it has to be ensured during feeding, whatever the circumstances, that from the closed liquid system no liquid can find its way into the source from which feeding takes place, for instance as a result of a pressure increase in the liquid system or a pressure reduction or pressure failure in the liquid source. It also has to be ensured that when a calamity occurs, for instance pipe fracture in the liquid system, the supply from the liquid source is cut off at least to a substantial degree, so that the calamity is not made even worse.

[0003] By way of example, the problems will be discussed in more detail with reference to a central heating installation. Such closed liquid circulation circuits with varying temperature and pressure often utilize an expansion tank, so that in case of temperature variations expansion and reduction of the enclosed liquid volume can be met without excessive pressure increase. Furthermore, the fact occurs that in such a closed liquid circulation circuit, in particular when a central heating installation is involved, loss of liquid from the closed circuit can hardly be excluded. So much liquid can then escape from the closed system that the leakage becomes clearly visible and can therefore be remedied. When the amounts are smaller, the location of the leakage can hardly be detected or can be detected only with great difficulty. Furthermore, the escaping amount of liquid may be so small that the liquid fully evaporates nearly immediately, in which case sweat leakage losses are involved that are hardly, if at all, traceable. When carying out prolonged measurements at a heating installation of 40 kW, it was found that these non-traceable sweat leakage losses were about 0.8 cc/24 h, which corresponds to about 300 cc in one heating season.

[0004] The water leaking away with or without notice can be collected to a specific degree by the expansion tank, which can be regarded as a make-up source, but then as an only restricted or limited make-up source. If this source is exhausted, then on farther leakage the pressure in the closed liquid circulation circuit will be able to fall rapidly, which, in case of falling below a specific pressure, or instance when the pressure in a heating installation falls to atmospheric pressure, leads to automatic out-of-operation of the installation. For a central heating installation, this may have disastrous consequences, for instance during a frosty night. This can be prevented by means of a make-up method as known from WO-A-00/19149. This method, however, requires special provisions to prevent, as discussed above, liquid from flowing back from the dosed liquid system to the liquid source, and most certainly to prevent in case of, for instance, pipe fracture in the closed liquid system liquid from freely flowing in from an actually unlimited liquid source, the public water supply system.

[0005] The object of the invention is to provide a method with which a closed liquid system is automatically fed from a liquid source according to need, without involving the risk that liquid can find its way from the liquid system into the liquid source, and in which it is also ensured that in case of a calamity in the liquid system liquid cannot be passed without restraint from the liquid source to the liquid system.

[0006] A further object of the invention is to provide a method with which a predetermined limited amount of liquid can be instantaneously fed to the liquid system.

[0007] An object of the invention also is to provide a drip feeder with which a method as referred to above can be carried out advantageously, which drip feeder can therefore automatically make up minor amounts of liquid escaping from the closed circulation circuit according to need from an essentially unlimited source, such as a public water supply system, and that without involving a risk of repulsion or unchecked expulsion.

[0008] A further object of the invention is to provide a closed liquid circulation system, which, by utilizing such a drip feeder, can be held under pressure automatically, while, furthermore, it can be ensured that when a leakage occurs a specific and limited amount of liquid can be momentarily expelled to facilitate the detection of the location of leakage, after the expulsion of which limited amount of liquid the automatic feed does not lead to a continuous extra water expulsion.

[0009] By arranging according to the invention in a method for automatic y feeding a closed liquid system from a liquid source according to need that the liquid buffer is created between the liquid source and the closed feed system and from the feed buffer to the closed liquid system only dropwise liquid transport is admitted, it is ensured that the liquid circuit can be continuously fed from the liquid source, while, simultaneously, it is arranged that pressing back liquid to the liquid buffer is limited and backflow of liquid to the liquid source is always fully excluded. It is then also ensured that despite the fact that during normal operation liquid can be allowed to flow in from the liquid source continuously and without supervision, in ease of pressure reduction or pressure failure in the liquid circuit, for instance as a result of a pipe fracture, further liquid can leak away from the liquid source only dropwise, until the time is found to completely close down the supply in another manner, for instance through a valve.

[0010] The feed buffer can then be in open communication with the liquid system, therefore actually form part thereof. In that case the feed buffer can be subject to pressure fluctuations, and according to a farther embodiment of the invention it is preferred that the feed buffer has a minimum volume, which is increased when the pressure in the feed buffer exceeds the pressure in the liquid source. Thus, an expansion possibility is arranged for the feed buffer, and it may further be arranged that increase in the volume of the fed buffer is limited by a blow-off excess pressure protection.

[0011] Because liquid can be given off by the feed buffer only dropwise, an efficient outflow protection has indeed been obtained, but the amount of liquid that can be added to the system per unit of time is limited. If it is deemed desirable that in a relatively short time a large amount of liquid can de delivered to the system, this can be realized according to a further embodiment of the invention if between the feed buffer and the closed liquid system a liquid stock is created, which is fed via an open connection through dropwise transport from the feed buffer, and which is connected with the liquid system via a closable passage, while the opening and closing of the passage is controlled depending on magnitudes generated by the closed liquid system.

[0012] To realize the invention, there can be advantageously utilized a feed buffer that is accommodated in a drip feeder provided with a cylindrical housing with an inlet, an outlet and a substantially cylindrical plunger arranged in the housing so as to be freely movable, which plunger, provided with at least a first part fitting into the cylindrical housing with sliding fit and a second part having a smaller diameter than the first part, can close the outlet in an abutting position while leaving clear a minuscule leakage channel and is provided with a passage that can connect the inlet with a space in the housing around the second part and is provided with a non-return valve preventing flow from the space to the inlet. Through these measures a drip feeder is obtained in which, after connection to a liquid source under pressure, such as a public water supply system, the plunger is driven into the abutting position by the liquid pressure, with the minuscule leakage channel being of such design that it passes liquid dropwise in a limited amount only. Thus, small sweat leakage losses can be automatically and continuously made up. If a great calamity should occur, for instance pipe fracture, resulting in a pressure failure at the outlet of the drip feeder, this drip feeder continues to deliver liquid only dropwise notwithstanding, so that the consequences of the pipe fracture cannot be made even worse through a continuous supply of larger amounts of make-up liquid. If the reverse occurs, that is to say a higher pressure at the outlet than at the inlet, for instance in case of a temporary pressure reduction or pressure failure in the make-up source, the non-return valve prevents liquid from passing this valve and thus finding its way into the make-up source via the inlet, even if the pressure difference between the outlet and the inlet increases so much that the plunger is pressed in the direction of the inlet and the minuscule leakage channel turns into a wider open connection.

[0013] The realization and proper dimensioning of the minuscule leakage channel and the maintenance thereof in dimensioned condition depends, inter alia, on the manner in which the second part of the plunger cooperates with the outlet. To optimize that cooperation, it may be arranged according to a further embodiment of the invention that the second part of the plunger is extended by a centrically placed pin-shaped projection, which, with sliding fit, engages a bore forming part of the outlet and is provided near the connection to the second part with a circumferential groove, to which at least a longitudinal groove extending in the longitudinal direction of the pin-shaped projection connects. Through these measures both an accurate guidance of the plunger in the housing and a reduction of the outlet to the dimensions desired therefor is realized.

[0014] The minuscule leakage channel can be realized in many ways. An example thereof may be extremely fine grooves in one or both cooperating end faces of the second part of the plunger and an end wall of the housing. According to a farther embodiment of the invention, however, it is especially preferred that the pin-shaped projection connects to the second part of the plunger with a foot part and terminates in a free end, with a sealing ring being arranged around the foot part and the free end in the abutting position of the second part contacting a cam face of an adjusting element, which is movable relative to the pin-shaped projection and, when moved, can shift the plunger via the pin-shaped projection in the longitudinal direction. Through these measures a structure is obtained with which the degree of leakage, and therefore the width of the minuscule leakage channel, can be very accurately adjusted. Normally, the sealing ring is pressed by the plunger into a sealing position against the end wall of the housing. With the adjusting element, however, the plunger can be pressed back, as a result of which the initially more flattened sealing ring increasingly begins to assume its rounder issuing form again. At a given moment, this has the result that the sealing ring no longer seals completely, but releases minuscule leakage passages. The width of the leakage passages to be thus obtained, together forming the minuscule leakage channel, can be accurately controlled by means of the adjusting element.

[0015] As stated before, during use of the drip feeder the plunger is urged into the abutting position through the liquid pressure from the make-up source. To be always sure, also in case of a temporarily lower pressure or pressure failure in the make-up source, that the plunger is maintained in its abutting position, a supplementary force towards the abutting position has to be exerted on the plunger. This can be easily realized if according to a further embodiment of the invention the plunger is pressed into the abutting position by a spring, which is supported on the plunger, on the one hand, and on a stop part stationarily connected with the housing, on the other hand, in which connection it may further be preferred that the stop part is adjustable relative to the housing.

[0016] In a relatively easy manner, according to a further embodiment of the invention, a very effective non-return valve can be realized if it is formed by an annular groove in the outer surface of the second part of the plunger, which groove is provided with side edges and a bottom, into which at least a passage communicating with the inlet opens, and is sealed at a distance from the bottom by an 0-ring abutting on the side edges. Moreover, by further designing the side edges of the groove so as to be adjustable relative to each other, the opening pressure of the non-return valve can be optimally adjusted, for instance such that the non-return valve already opens at a pressure in the inlet that is only a little higher than the pressure in the space around the second part, while it still remains ensured that the non-return valve is optimally blocked if the pressure in the space exceeds the pressure in the inlet. Also, the non-return valve can be adjusted to a higher opening pressure, for instance if it is desired that the maximum feed pressure of the liquid added to the liquid circulation system is lower than the pressure in the inlet.

[0017] In the foregoing, it has already been noted that it is desirable, or may even be required because of government regulations, that no liquid can be pressed from the liquid circulation system into the make-up source, for which purpose the non-return valve present is a very effective means. If in the liquid circulation system, through unexpected causes, for instance failure of an excess pressure protection valve, such a high pressure should be built up in the liquid circulation system that the plunger is pressed in the direction of the inlet for a specific distance, as a result of which, for instance, the pin-shaped projection could leave its guide, then a relief of the system can be advantageously realized with the drip feeder according to the invention if according to a further embodiment the housing is provided with an outlet, which is sealingly closed by the first part of the plunger if the second part of the plunger is in the abutting position, and which is released after a predetermined movement of the plunger in the direction of the inlet.

[0018] The invention also relates to a heating installation provided with a closed liquid circulation circuit, in which at least a boiler and an expansion tank are accommodated, and which closed liquid circulation circuit is connected via a drip feeder according to the invention to a liquid source under pressure. Apart from extreme calamities, there is thus obtained a heating system that does not become inactive for lack of water resulting in too low a system pressure and hence automatic out-of-operation.

[0019] To detect a leakage in the liquid circulation circuit, it may be very helpful if the amount of liquid flowing out of the leakage is such that the location of the leakage becomes clearly visible. According to a further embodiment of the invention, this observation can be promoted if the outlet of the drip feeder is in open communication both with a make-up line for the closed liquid circulation circuit and with an inlet for a storage container for make-up water, with the make-up line connecting to the inlet of a make-up element, which is in open communication with the liquid circulation circuit, which inlet is provided with a valve, which is normally in a closed position, but opens in case of lack of water in the liquid circulation circuit. Through these measures a specific amount of liquid can be kept available in the storage container under a specific pressure, which can be fed to the liquid circulation circuit momentarily when opening the valve of the make-up element. Through this liquid pulse a leakage can be made visible. Also, this is, however, only a momentary liquid pulse. For if the storage container has been emptied, the pulsewise supply stops and further make-up only takes place via the drip feeder. Thus, a leakage place can be made visible, but, moreover, excessive continued leakage of the liquid circulation system through this making visible is prevented.

[0020] With reference to embodiments shown in the drawings, the drip feeder and the heating system according to the invention will now be discussed in more detail, though exclusively by way of non-limiting examples. In these drawings:

[0021]FIG. 1 is a cross-section of a chip feeder;

[0022]FIG. 2 is a detail of FIG. 1 an an enlarged scale; and

[0023]FIG. 3 is a diagrammatic view of a heating system.

[0024] The drip feeder shown in FIG. 1 comprises a cylindrical housing 1 with an inlet 2 and an outlet 3. Slidably arranged inside the housing 1 is a plunger 4, which plunger 4 comprises a first part 4 a, a second part 4 b and a pin-shaped projection 4 c.

[0025] The first part 4 a is internally provided with a chamber 5 for accommodating and, with interposition of a filter plate 20, supporting an end of a spring 6, which is further supported on an annular stop part 7 movably arranged in the housing 1. The outer circumferential surface of the first part 4 a moves with sliding fit along the inner wall of the cylindrical housing 1, while seating rings 8 sealingly separate the spaces in the housing 1 to the left and right of the first part.

[0026] The second part 4 b of the plunger 4 has a smaller diameter than the first part 4 a, so that a space 9 is formed around the second part 4 b inside the housing 1. Provided in the outer circumferential surface of the second part 4 b is a groove 10, into the bottom of which passages 11 open, which issue from the chamber 5 in the first part 4 a. On the outer circumferential surface of the second part 4 b the goove 10 is shut off by an O-ring 12. Thus, a non-return valve is formed, because at a higher pressure in the chamber 5 than in the space 9 the O-ring 12 will move outwards and releases the connection between the chamber 5 and the space 9, while at a higher pressure in the space 9 than in the chamber 5 the O-ring 12 is pressed more firmly and hence more sealingly into the groove 10. The opening pressure of the non-return valve is adjustable, because one of the wall of the groove 10 is formed by an end edge of a nut part mounted by screwing on the remaining part of the second part 4 b so as to be displaceable, which second part 4 b is sealed by a sealing ring 19 relative to the nut part. The second part 4 b carries the pin-shaped projection 4 c, which extends with sliding fit into a bore forming part of the outlet 3. As FIG. 2 clearly shows, the pin-shaped projection 4 c is provided with a circumferential groove la, into which a longitudinal groove 14 opens. Around the pin-shaped projection 4 c and in contact with, on the one hand, the second part 4 b and, on the other hand, the housing wall, a sealing ring 15 is provided. The pin-shaped projection 4 c is provided with a free end in the form of a conical surface with a rather large, obtuse apex. The conical surface is in contact with a cam face lea of in adjusting element 16, which extends transversely to the pin-shaped projection 4 c and is adjustably arranged in the housing 1 in the longitudinal direction and is sealed relative to the surroundings by a sealing ring 21.

[0027] The housing 1 is further provided with an internal ring groove 17, which communicates with a drain 18 leading to the surroundings.

[0028] The operation of the drip feeder is as follows.

[0029] The inlet 2 is connected by means not shown to a liquid source under pressure, for instance a public water supply system. Through this pressure in cooperation with the force exerted by the spring 6 the plunger is pressed to the right into the position shown in FIG. 1. If the liquid pressure in the chamber 5 is higher than the liquid pressure in the space 9, this will have the result that the O-ring 12 moves outwards and liquid flows from the chamber 5 to the space 9. To feed a liquid circulation system connected to the outlet 3 in a manner not shown, liquid will have to be able to flow from the space 9 to the outlet 3 and will therefore have to pass the sealing ring 15. This has been made possible by forming a minuscule leakage channel at the location of the sealing ring 15 by pushing back the plunger 4 via the adjusting element 16, such that the sealing ring 15 relaxes such, that is to say springs back from its flatter sealing configuration into a rounder configuration, that along the sealing ring minuscule leakage passages are formed liquid leaking therethrough finds its way into the circumferential groove 13 and flows via the longitudinal groove 14 to the outlet 3. By properly adjusting the adjusting element 16 it is thus realized that liquid is given off dropwise. By giving off liquid to the liquid circulation system the pressure in the space 9 will decrease, after which making-up from the chamber 5 takes place again via the non-return valve.

[0030] If owing to special circumstances the liquid pressure in the outlet 3 exceeds the liquid pressure in the space 9, the non-return valve prevents liquid from entering the chamber 5 from the space 9. If the pressure difference between the outlet 3 and the inlet 2 increases so much that the plunger 4 in its totality is urged to the left, that is to say in the direction of the inlet 2, then after a specific movement of the plunger 4 the space 9 will enter into communication with the ring groove 17 and the pressure will be blown off outwards via the outlet 18.

[0031]FIG. 3 shows a heating system comprising a closed liquid circulation circuit 20 with radiators 21 and a boiler 22. A membraneless expansion tank 24 connected to the liquid circulation circuit 20 via an air collector 23 is equipped with an element 25 provided with a make-up valve 26 and a deaerating valve 27. The valves 26 and 27 are normally in closed condition and can be opened by a float in the expansion tank 24, while through a fall of the liquid level in the expansion tank 24 as a result of the escape of liquid from the closed liquid circulation system 20 the co-falling float will open the deaerating valve 27 after reaching a first level and the make-up valve 26 in case of a further fall to a second level. To the make-up valve 26 a make-up line 28 connects, which is in open communication with, on the one hand, a drip feeder 29 connected to a line So of a public water supply system and, on the other hand, a storage container 31.

[0032] Through sweat leakage losses the float in the expansion tank 24 will at a given moment fall so far that the make-up valve 26 is opened and water is supplied from the storage container 31, after which the make-up valve closes again and the water withdrawn from the storage container 31 is made up again by the drip feeder 29. The advantage of using the storage container 31 in combination with the drip feeder 29 is that in spite of the dropwise supply of the liquid a specific stock of make-up liquid under high pressure is always immediately available. This amount of liquid is immediately available if a calamity occurs, for instance in case of accidental lack of water. The limited expulsion from the storage container 31 prevents further damage and, through the liquid pulse, immediately shows the location where a repair has to be carried out.

[0033] It is self-evident that within the framework of the invention as laid down in the appended claims still many modifications and variants are possible. Thus, the invention has been explained above with reference to a central heating installation. Similarly, however, use in other liquid systems and production processes is possible, in which feeding with, in particular, relatively small amounts of liquid is necessary, for instance to meet leakage or sweat losses or to supply additives. If it is sufficient to supply dropwise, a feed buffer or a drip feeder may be in open communication with the liquid system. If the supply of larger amounts of liquid than drip feed can provide is deemed desirable or specific periods, use may be made of a liquid stock to be brought into open communication with the liquid system at the desired times, which stock has been built up and is made up by the drip feed. 

1: A method for automatically feeding a closed liquid system from a liquid source. 2: A method according to claim 1, characterized in that the feed buffer has a minimum volume. 3: A method according to claim
 2. 4: A method according to claim
 1. 5: A drip feeder provided with a cylindrical housing with an inlet. 6: A drip feeder according to claim
 5. 7: A drip feeder according to claim
 6. 8: A drip feeder according to claim
 5. 9: A drip feeder according to claim
 8. 10: A drip feeder according to claim
 5. 11: A drip feeder according to claim
 10. 12: A drip feeder according to claim
 5. 13: A heating installation provided with a closed liquid circulation circuit. 14: A heating installation according to claim
 10. 